Knife Shop

[Art]

This thread is sort of my knifemaking/sharpening blog.

I make the occasional knife, most of them tactical ones for friends kids and grandkids who are just graduating from basic or advanced training. I mostly sharpen scissors (from standard to technical stylist scissors/shears, to a pair of Fiskars), knives, hand and power tools, leatherworking tools, most garden tools (please don't bring a 1,000 lb garden tractor over here with the mower blades attached), Dog and human hair clippers and blades (sharpening and repair), I'll tackle most anything if you are in a bind, but I will send out saw blades and end mills as there are others who can do them better.

That being said, I am retired. I don't have to do anything If I don't want to, I do it just to do something that I know how to do. We all like to feel useful, but I ain't going to work myself to death.

This is kind of the see something, say something of a knife shop. Everyone is welcome to add to or ask questions.

Art

[Art]

Just how darned sharp can you get it, and the hunter from hell.

Today started out just fine; I have a ton of work backed-up but nothing I can't handle. I do things one at a time, or one job at a time. I usually charge $5-$10 to sharpen a knife, depending on complexity. A head knife is kinda at the top of the scale at $10, and a regular old kitchen knife is usually $5.

I've got this hunter to do, and then some head knives. Oh yes, this is the hunter from hell. This is a custom hunter from a dead maker. Owner says it won't stay sharp. This isn't unusual as there are a ton of things that can be tricky along the way. Things that happen are when the owner changes things. This was the case here.

I examined the knife and found that it had a burr like the hook on a cabinet scraper, big ole honkin burr. The knife was hollow ground and pretty thin at the edge. I couldn't tell the included angle exactly, but it was well south of 15°. This is ok for cutting fresh meat, no bones, and butter. When the edge was new, it probably shaved hair like a barber. Anything other than that and the edge is going to roll over (and in this case play very dead). So after contacting the owner, I proceeded to spend the next 5 hours (yes, it was all hand work on a finished knife) getting the edge to where there was something behind it.

The lesson here is sharp is not necessarily durable. A 20° included angle is maybe as acute as it should be. But 20° is mighty thin behind the edge, even with a convex edge. The newer "high tech" steels of today do not take too well to 20° or even 25°. You won't get much rollover at 25° but the edge will often chip out; not big honking chips but you can see it with the unaided eye. Included angles of 30° and even 35° are needed for HRc 59 and above steels that are going to see some work. Finding that perfect angle is mostly trial and error, and keeping the use factor in a narrow range (like for cutting leather only) will allow you to modify the angle for a sharper knife in a particular category.

Just keep in mind that 16° is a straight razor, and those edges, (even of hand forged high carbon steel where they can pack the edges) are just not that durable and require stropping all the time when just slicing hair (and occasionally skin). A straight razor will not get 2 or three inches into hard leather before the edge rolls over and just plain stops cutting.

Art

[Oldtoolsniper]

Art,

I really appreciate you taking the time to explain this stuff. I like the fact that you don't just say "sharpen at this angle" you explain why. It's almost like you want to know what the customer intends to use the cutting edge for and its sharpened for that purpose. Could it be that a cutting edge is actually a specialized tool? Imagine that.

[mishkin]

Art, thank you so much for posting this and opening the whole section in general.

Do you know what are the most common angles for cutting tools in leatherworking? Round knives, skiving knives, french edgers, etc.

[Art]

Off the top of my head?

Head Knives -- 30°

Skiving Knives can go 20° to 25°, or even 30°. This depends very much on the steel. Most of the time, these knives are single bevel, and can be pretty thin, but I have a few that are 20° on the single bevel and then a micro bevel of 23° to 25°. Some not really leather tool makers cut a back bevel usually 12.5° to 15° on a side. I haven't used enough of these to figure out the why and wherefore of the back bevel. We do this on plane blades, but it is really a clearance thing there. Since the skiving knife works alone (without the big body of the plane to mess with the chips etc), I'm not seeing it.

French Edgers (well any edger) -- I generally go with the design of the tool, or he who went before me. There are many designs of edgers and most of the time, you go with the flow. Just because it works, 30° included is a starting point for darned near anything, then go up or down from there depending on the use of the tool.

I can sharpen any of my tools down as low as 20° depending on the ability of the steel to hold together, but I am going to have to sharpen a lot more often. Some really fine air hardening steels like A2 can't handle 20° and aren't that great at 25°, but do fine at 30° and maybe a 35° micro bevel on top of that. Micro bevels are more the realm of hand sharpeners who use them to more quickly cut a new edge or hone an old one.

To get a good idea of how to sharpen something, look at it closely and determine how you will put an edge on the tool that looks pretty much like what it came with. If it is a bloody stub, think 30°.

Art

[Oldtoolsniper]

Just for clarity when you say 20° it's the total bevel, correct? On a single bevel the bevel would be sharpened at 20°, on a double bevel it would be each bevel sharpened at 10° to make 20°. Is this correct?

[Art]

It depends on whether the tool is single or double bevel. If it is single bevel, 20° means 20° per side, the only side. For double bevel, 20° to me means 20° included, or 10° per side.

Be careful with the acute included angles like 20°, many of today's steels just won't handle it. Steels that hover around the eutectic are more a candidate for this experiment. O-1 has been a good candidate, but I have never found anything over 1% carbon that will hold 20°.

I'd say to stick with higher numbers with any stainless steel, even D-2 (which is an "almost" stainless steel).

Art

[Kulafarmer]

Art, thank you,,, good info,

Was curious if 304 or 410 stainless could be used to make a round or head knife? Can get sheet stock and get it water jet cut thrn do the grinding etc, but not sure if the stock is really suitable for this

[Art]

304 stainless is good for kitchen sinks and equipment. It is typical 18/8 stainless and is austenitic (non magnetic), the only knives it is good for is flatware.

410 is martensitic (magnetic) but just doesn't have enough carbon to make the grade for most knives, except cheap ones.

You can get sheet stock in various knife steels and have it water jet, plasma, or laser cut. Steels I would recommend are 440C, BG-42, 154CM, ATS-34, D-2, for stainless/semi-stainless, and O-1, 1075, 1085, 52100, 1095, and L-6 and O-6 for other than stainless. You need to select a steel for the type of knife you are making and your capabilities for working it.

Art

[Kulafarmer]

Thank you art, is exactly the info i was looking for,

[mishkin]

Thanks, Art. I checked couple of the skiving knives that I have and both had 17.5 angle. No wonder I'm stropping all the time =)

[Art]

Even at 20 to 30, you really need to strop often. More So around 20.

Art

[judgebc]

Art,

I have been sharpening my Tandy swivel knife blade and can’t seem to hold a steady angle.

My blade is polished but my sharpening is not in one plane.

Tandy has a jig, but I don’t see how you can set it at a pre-determined angle?

How do you sharpen a Swivel Knife? Thanks

[Art]

Hi Judge,

First, included angles. I have seen swivel knives with anywhere from 40° to as high as 60° included angles. That's 20° to 30° per side. I try to duplicate the original angle if it still exists, if not, go with 45°. Most folks use the Keen Edge swivel knife sharpening jig, and watch this video of Kevin Hopkins of SLC showing you how to use it. The amount the blade sticks out from the jig determines the angle. Try to match the original angle, it makes the job go a lot faster as there is less metal to remove. Some of these custom maker blades are made of OhMyGhodium and the less of that stuff you have to remove, the better. Bruce Cheaney also has a video that doesn't use a jig. The facet on a swivel knife blade is usually so large that it is pretty easy to sharpen without a jig, but nobody is going to fault anyone for using one. I use one. The more the facets look like mirrors, the better the knife will cut.

Art

[rickdroid]

Art,

I have been sharpening my Tandy swivel knife blade and can’t seem to hold a steady angle.

My blade is polished but my sharpening is not in one plane.

Tandy has a jig, but I don’t see how you can set it at a pre-determined angle?

How do you sharpen a Swivel Knife? Thanks

I've got a Tandy jig for sharpening swivel knives, if you care to borrow it PM me with a mailing address and I can get it in the mail in a couple of days.